WO2004106266A1

WO2004106266A1 - A method of manufacturing coated ceramic products

Info

Publication number: WO2004106266A1
Application number: PCT/PL2003/000046
Authority: WO
Inventors: Andrzej Oleksiewicz; Leszek Celuch; Krzysztof Krolak; Adam Rozalski; Mieczyslaw Wolski; Krystyna Wodnicka
Original assignee: Andrzej Oleksiewicz; Leszek Celuch; Krzysztof Krolak; Adam Rozalski; Mieczyslaw Wolski; Krystyna Wodnicka
Priority date: 2003-05-29
Filing date: 2003-05-29
Publication date: 2004-12-09
Also published as: AU2003251248A1

Abstract

The method consists in forming products from the body and advantageously one-side coating with a water suspension of the body. The slip of grain-size distribution defined by sieve residue from 15,0 to 0,1% on a 0,063 mm mesh and density ranging from 1,2 to 1,85 g/cm3 is divided by forcing and/or sedimentation process into at least two grain fractions of the lower grain size limit of 25,0 µm and density from 1,15 to 1,30 g/cm3, while the second layer from the suspension of graining up to 6,0 µm and density from 1,01 to 1,2 g/cm3. Finally the product is fired.

Description

A Method of Manufacturing Coated Ceramic Products

The subject of this invention is a method of manufacturing coated ceramic products, in particular those used in building industry for roof covering, facade cladding and internal wall lining.

There is known a ceramic product manufacturing process, especially that of facade cladding tiles, consisting in forming products from a ceramic body, coating it with a glaze and firing once or twice at temperatures ranging from 1150 K to 1700 K. The glaze is made by apply a suspension of fine powdered glass onto the body. The glass is manufactured in an energy intensive melting process from a specially selected glass batch in appropriate large-size gas fired continuously running furnaces. Liquid glass body is broken up with simultaneous wet toughening in water, or in dry process by using intensively cooled rolls. The obtained frit is mixed with additives and colored oxides, suspended and applied to the tile surface. The tiles are then fired.

There is also known an engobe method consisting in applying a layer of white or colored clay and firing. The body and coating layer are made of different materials. In addition, a ground ceramic frit is added to clay suspension to enhance coating quality.

The method covered by the invention consists in forming products from raw ceramic plastic slip or dry granulates and coating advantageously its surfaces with a one-side coating of ceramic body made from identical raw materials suspended in water. The slip of grain-size distribution defined by 15,0 to 0,1% sieve residue on a 0,063 mm mesh and density ranging from 1,2 to 1,85 g/cm³ is forced to splitting up into at least two fractions and/or subjected to sedimentation process at the lower limit of coarse fraction of 25,0 μm. Then, the product is coated by employing any method with a water suspension of grain-size distribution up to 25,0 μm and density ranging from 1,01 to 1,30 g/cm³. If double coating is made, the first layer is applied with suspension of 4,0 to 25,0 μm in graining and 1,15 to 1,30 g/cm³ in density, while the second layer is made from suspension of grain-size distribution up to 6,0 μm and density ranging from 1,01 to 1,2 g/cm³.

The natural color of the ceramic substrate is advantageously left unchanged, while the suspension forming the top layer can be stained in any color. The grained body for ceramic product coating has the internal surface area advantageously extended above 50 m²/g as calculated from Brunaer-Elmmet-Teller formula. The selected surfaces of ceramic products can be coated with ceramic body suspension in different colors.

Finally, the products are fired.

Surprisingly, the method presented above brings an unforeseen advantage, namely a coating layer manufactured in relatively simply cost-effective and integrated process, and of quality similar to glazes and highly exceeding that of engobes.

In terms of smoothness and integrity the coating layer resembles the glazed surface but exceeds it considerably in manufacturing process effects. The selection of glaze for an appropriate ceramic body is a complicated task. Inadequate glaze quality or improper selection for given composition and properties of the body leads to various defects resulting in significant share of rejects or lower quality products.

Typical glazes has no resistance to low temperatures and high temperature fluctuations and special glazes are therefore developed for ceramic products used under such conditions. The method covered by this invention requires no such much attention and precision in coating selection as those of glaze. In addition, ceramic coating is less vulnerable to ambient conditions than the glaze.

The coating layer obtained from the method covered by this invention features a lower water absorbability than engobes while its stainproof and self- cleaning properties are similar to those of glazes. There are evidences indicating higher durability of the obtained coating compared to that of glazed surfaces under ambient conditions.

The obtained coating is a mat surface with a slight gloss, thus excellent for roofing tiles and facade claddings. The coating is naturally colored in brown, but the suspension can be stained in different colors to add decoration. The solution covered by this invention is illustrated by examples of fabrication.

Example 1

A slip for roofing tiles is prepared. The same slip of medium-size graining, defined as 11% sieve residue on a 0,063 mm mesh, suspended with water to the density of 1,3 g/cm³ is divided into two fractions of 25 μm in boundary grain size. The coarser fraction is added to the roofing tile body, while the finer fraction of internal surface area extended above 50 m /g as calculated from Reunauer-Elmmet- Teller formula is forced to splitting up into two fractions. The fraction of graining from 6,0 to 25,0 μm is suspended in water to the density of 1,18 g/cm³ and applied on the roofing tile external surfaces. The fraction of graining up to 6,0 μm is suspended in water to the density of 1,1 g/cm³ and applied on the roofing tile coating made in previous step.

Due to its high flowability the suspension drips onto roofing tile side surfaces.

Finally, the roofing tiles are fired at approx. 1360 K.

The finished roofing tiles have a clearly rough brown colored underside surface, while its top and side surfaces are much more smoother and naturally colored in brown.

Example 2

A ceramic body is prepared from dry granulates and facade tiles are formed by pressing.

At the same time a body is prepared for facing layer by grinding ceramic raw materials. The resulting powders are thoroughly mixed and suspended in water to the density of 1,5 g/cm³. The suspension is fractionated into two fractions of 14 μm in boundary grain size. The coarser fraction is reused for preparing the slip for tiles. The slip of graining determined by internal surface area extended above 50 m²/g as calculated from Brunauer-Elmmet-Teller formula is divided into three portions. Each of them is thoroughly mixed with different pigment and suspended in 95 water to the density of 1,07 g/cm³ and then applied on the external surface of the same tile. Due to suspension low density and application on the same surface, the different colors are mixed within its boundary layers. The suspension flowability cause dripping on tile side surfaces thus forming a coating layer.

Finally, the tiles are fired at approx. 1200 K.

100 The finished tiles have clearly rough brown underside surface, while its top and side surfaces are much more smoother and stained in three intermingled colors, thus adding decoration and attractive visual effects.

Claims

105 A method of manufacturing coated ceramic products consisting in preparing a ceramic slip or a body from dry granulates, product forming and applying advantageously a one-side coating with the body water suspension, thus forming a coating layer, and firing products at temperature ranging from 1160 to 1400 K, characterised in that the slip of grain-size distribution defined by sieve

110 residue from 15% to 0,1% on a 0,063 mm mesh and density ranging from 1,2 to

1,85 g/cm is prepared advantageously from the same raw materials as those of the body, and is forced to splitting up and/or broken up by sedimentation process into at least two fractions, while the lower limit of coarser fraction is fixed at grain size of 25,0 μm; the product is then coated by employing any method and

115 applying the water suspension of graining up to 25,0 μm and the density range of

1,01 to 1,3 g/cm³ once or twice; for double application the first layer is made from the suspension of grain-size distribution ranging from 4,0 to 25,0 μm and density from 1,15 to 1,30 g/cm³; the second layer is applied with the suspension of graining up to 6,0 μm and density from 1,01 to 1,2 g/cm³ and finally, the

120 product is fired.

2. A method as recited in claim 1, characterised in that the suspension for coating ceramic product has internal surface area extended above 50 m/g as calculated from Brunauer-Elmmet-Teller formula.

3. A method as recited in claim 1, characterised in that the natural body 125 color is maintained, while the suspension used for top coating can be stained in any color.

4. A method as recited in claim 3, characterised in that the selected product surfaces are coated with ceramic body suspensions stained in various colors.